Integrated water treatment and flue gas desulfurization process

Abstract

A water stream containing hardness minerals is subjected to a water treatment process using an alkali agent to precipitate the hardness minerals and to produce a softened water stream is used to create an integrated water treatment and flue gas desulfurization process. Thereafter, the softened, alkaline water stream is utilized in a scrubber to scrub a flue gas containing sulfur dioxide to produce a sulfur-lean flue gas. The invention may be applied to a steam-based bitumen recovery operation where bitumen, sour produced gas or other sulfur containing fuels are burned for producing steam for bitumen recovery. More specifically, the associated produced water from the bitumen recovery process may be softened for re-use and for utilization as a scrubbing agent for high-sulfur containing flue gas arising from the steam generators. The process provides an economically favorable process while minimizing waste disposal requirements.

1. An integrated water treatment and flue gas desulfurization process comprising:
 (a) subjecting a water stream containing hardness minerals to a water treatment process using an alkali agent to precipitate the hardness minerals and raise the pH of the water stream to at least about 8.5, thereby producing a softened alkaline water stream having a pH of at least about 8.5; and 
 (b) utilizing the softened alkaline water stream having a pH of at least about 8.5 to scrub a flue gas containing sulfur dioxide to produce a sulfur-lean flue gas, wherein said flue gas containing sulfur dioxide is produced by burning a high-sulfur fuel. 
 
     
     
       2. The process of  claim 1  wherein the precipitating alkali agent is ammonia or aqueous ammonia. 
     
     
       3. The process of  claim 1  wherein step (a) comprises the addition of sodium carbonate, carbon dioxide, sodium hydroxide, or magnesium oxide, or any combination thereof. 
     
     
       4. The process of  claim 3  wherein the CO 2  can be a slipstream of the treated flue gas. 
     
     
       5. The process of  claim 1  wherein the process is integrated with a steam injection bitumen recovery operation where step (b) further produces a treated water stream rich in sulfite/bisulfite for steam generation and underground steam injection and the water stream for step (a) is a produced water stream recovered from an underground reservoir. 
     
     
       6. The process of  claim 5  wherein the treated water stream has a pH of at least 6.8 and not more than 7.2. 
     
     
       7. The process of  claim 1  wherein step (a) includes a separation process to separate mineral precipitates from the softened water stream. 
     
     
       8. The process of  claim 1  wherein the water stream for step (a) has a temperature of at least 85 degrees Celsius and not more than 100 degrees Celsius. 
     
     
       9. The process of  claim 1  wherein step (a) includes addition of carbon dioxide gas or sodium carbonate as a source of carbonate for precipitating calcium carbonate. 
     
     
       10. The process of  claim 1  wherein the alkali precipitating agent is a combination of excess ammonia and magnesium oxide. 
     
     
       11. The process of  claim 1  wherein in step (a) the pH of the water stream is raised to at least 9.3. 
     
     
       12. The process of  claim 1  wherein the high sulfur fuel is bitumen. 
     
     
       13. The process of  claim 1  wherein the high sulfur fuel is bitumen resid. 
     
     
       14. The process of  claim 1  wherein the high sulfur fuel is asphalt. 
     
     
       15. An integrated water treatment and flue gas desulfurization process comprising:
 (a) subjecting produced water containing hardness minerals and recovered from an underground reservoir in a steam injection bitumen recovery operation to a water treatment process using an alkali agent selected from the group consisting of ammonia, aqueous ammonia, and sodium hydroxide, and any combination thereof to precipitate the hardness minerals and raise the pH of the produced water to at least about 8.5, thereby producing a softened alkaline water stream having a pH of at least about 8.5; and, 
 (b) utilizing the softened alkaline water stream having a pH of at least about 8.5 to scrub a flue gas containing sulfur dioxide to produce a sulfur-lean flue gas and a treated water stream rich in sulfite/bisulfite for steam generation and underground steam injection, wherein said flue gas containing sulfur dioxide is produced by burning a high sulfur fuel. 
 
     
     
       16. The process of  claim 15  wherein step (a) includes a separation process to separate mineral precipitates from the softened water stream. 
     
     
       17. The integrated water treatment and flue gas desulfurization process of  claim 15  wherein step (a) includes the addition of magnesium oxide for silica removal. 
     
     
       18. The process of  claim 15  wherein step (a) includes the addition of carbon dioxide or sodium carbonate to enhance the precipitation of hardness minerals. 
     
     
       19. The process of  claim 15  wherein the high sulfur fuel is bitumen. 
     
     
       20. The process of  claim 15  wherein the high sulfur fuel is bitumen resid. 
     
     
       21. The process of  claim 15  wherein the high sulfur fuel is asphalt.